Although they existed in 1948 , Ball point pens as a signing medium were not commonly used yet, and they tended to write poorly and throw off globs of ink. The one pictured is pretty clean with the exception of the top part of the "C", its possible but unlikely it could have been signed at a later time as he died in 1954.
But will still go out on a limb and say its good , He was the guest of honor at the event and its unlikely that anyone who attended would have passed up an opportunity to get his autograph, BUT to be extra safe look at it under magnification and make sure its not a traceover, it dosen;t look to be in the scan but you can never be too careful
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jim@stinsonsports.com